JPS589441B2 - Servo control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a servo control method, and more specifically,
The present invention relates to a servo control device for a closed-loop positioning control system in which position feedback is always applied.

For example, in an electron beam exposure apparatus, the exposed object is
It is necessary to perform positioning quickly and accurately in (mm) steps, and for this reason a servo control device with position feedback is used.

In such a device, if you try to perform position control by giving the movement amount, which is the difference between the current position and the target position, as a step-like comparison position function, it will be difficult to control the position faithfully according to this comparison position function. In order to achieve this, it is necessary to use a mobile device with speed characteristics such that the maximum speed is almost infinite.

However, in reality, the maximum speed of the moving device is not so high, and its acceleration performance is also low, so as a result, vibrations occur in the vicinity of the target position, resulting in problems such as poor position control. arise.

For this reason, there is a method of providing a comparison position function in the form of a ramp to perform stable position control at the expense of responsiveness. Although the speed can be suppressed, the acceleration component cannot be controlled, and as a result, a large current flows through the power amplifier for the drive motor.

Therefore, an object of the present invention is to provide a servo control device that can perform positioning quickly and safely in a closed-loop positioning control system in which position feedback is applied.

A feature of the present invention for achieving the above object is that in a servo control device of a closed-loop positioning control system in which position feedback is always applied, positioning control of a controlled object from a first position to a second position is performed. means for generating a comparative position function having an acceleration component and a velocity component that do not exceed the maximum acceleration and maximum velocity of the device; means for generating a comparative velocity function based on the comparative position function; The present invention includes means for generating a comparison acceleration function, and a closed loop control device that performs a position control operation following the comparison position function, the comparison speed function, and the comparison speed function.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 shows a block diagram of an embodiment of a servo control device according to the present invention.

The servo control device 1 receives a target position set value X from a controller (not shown).

It has a comparison function generator 2 that generates a comparison position function, a comparison velocity function, and a comparison acceleration function, respectively, based on the comparison function generator 2, and a comparison position signal Xr, The comparison speed signal Vr of the analog signal and the comparison acceleration signal a of the analog signal are input to the closed-loop control device 3.

A closed-loop controller 3 receives each signal X from the comparison function generator 2.
A target position setting value X is set for a controlled object (not shown) following r, vr, and ar.

Move at the position indicated by .

In the closed loop control device 3, 4 is a comparison acceleration signal ar
and an acceleration deviation signal S1 from the controller 5; 6 is an amplifier; 7 and 8 are equivalent to a DC motor driven by the acceleration signal S2 amplified by the amplifier 6; 9 is an integrator that has a speed signal S3 and a position signal Sout obtained by detecting the rotational speed and amount of rotation of a DC moke rotating in response to a torque proportional to the acceleration signal S2, and 9 is a position signal Sout. .

The difference between u1 and the comparison position signal Xr is taken and the position deviation signal S
10 is an adder for obtaining the speed deviation signal S by taking the difference between the speed signal S3 and the comparison speed signal V.

The controller 5 obtains an acceleration deviation signal S1 using the position deviation signal S4 and speed deviation signal S5 to quickly converge these deviation signals to zero even in the event of an unexpected disturbance.

Since the closed loop control device 3 is configured as described above,
Of course, position feedback is applied.

In addition, the speed value at each point in time when the controlled object moves from the initial position to the target position is controlled to a predetermined state by the comparison speed signal Vr from the comparison function generator 2, and the comparison acceleration signal ar By adding the acceleration deviation signal ar and the acceleration deviation signal S1, the acceleration value at each time point becomes the comparison acceleration deviation signal ar
is controlled to a predetermined state.

As a result, a comparative position function, a comparative speed function, and
By predetermining the acceleration function and the comparison acceleration function, the object to be controlled moves in accordance with these functions and reaches a predetermined target position, making it possible to position the object extremely stably and quickly.

FIG. 2 shows in detail the comparison function generator 2 shown in FIG. 1, which generates each comparison signal based on each comparison function as described above.

The comparison function generator 2 includes a binary counter 11 in which the position data Xr before movement is preset as complementary binary data.

The position data xr from the counter 11 is input to an adder 12 to which a target position set value X0 given in the form of binary digital data is applied, and from the adder 12 a value corresponding to the value of X0-Xr is inputted. Difference data D1 in the form of binary digital data is output and input to the sign/negative determination circuit 13.

The positive/negative determination circuit 13 receives the difference data D1, that is, the switching control signal S6 which has a logical level of "1" when the value of X0-Xr is positive and "0" when the value of X0-xr is negative. A stop control signal S7 that becomes "1" is output only when the signal becomes O.

The difference data D1 is also input to the absolute value detection circuit 14.

The input/output characteristics of the absolute value detection circuit 14 are as shown in FIG. When it is outside, the output signal D2 has a constant positive value.

The output signal D2 is output in the form of a binary digital signal and is supplied to the ROM 15 as an address signal for the ROM 15.

A speed curve during deceleration is previously stored in the ROM 15 as data, and speed setting data D3 is output in accordance with the value of the output signal D2.

Reference numeral 16 indicates a target position setting value X.

This is a count pulse generator that starts oscillation when the count pulse generator 16 is applied, and the count pulse P1 from the count pulse generator 16 is input to the counter 17 and counted, and the count output data D4 from the counter 17 and acceleration setting data D3 is input to the comparator 18, and the comparator 18 compares which data has a larger value.

The counting output data D4 and the acceleration setting data D3 are input to the multiplexer 19 where switching is performed by the output signal S8 from the comparator 18, and when the value of the data D3 is larger than the value of the data D4, the data D4 is D/
input to the A converter 20, and the value of data D4 is the data D.
If the value is greater than 3, data D3 is input to the D/A converter 20.

The analog signal S9 from the D/A converter 20 is a voltage/
The signal is input to a frequency converter (hereinafter referred to as a V/F converter) 21 as a frequency control signal.

The V/F converter 21 is configured to stop its oscillation operation when the stop control signal S7 becomes "1", and the V/F converter 21 stops its oscillation operation when the stop control signal S7 becomes "1".
Pulse signal P2 from F converter 21 is sent to multiplexer 2
2 to the counter 11.

The multiplexer 22 sends the pulse signal P2 to the counter 11.
This is for supplying to either the addition terminal 11a or the subtraction terminal 1lb, and when the switching control signal S6 is "1"
In the case of , it is connected to the 1Ib side, and in the case of ``0'', it is connected to the 1Ib side.
Connected to side a.

The analog signal S9 is connected to one terminal 2 of the multiplexer 23.
3a, and is also supplied to the other terminal 23b via the inverter 24, and the multiplexer 2
The output from 3 is taken out as a comparison speed signal Vr.

The switching of the multiplexer 23 is also controlled by the switching control signal S6, and when the signal S6 is "1", the switching terminal 23c is connected to the terminal 23a, and when the signal S6 is "0", the switching terminal 23c is connected to the terminal 23a.
”, the switching terminal 23c is connected to the terminal 23b.

The comparison speed signal V, is differentiated by a differentiating circuit 24 and taken out as a comparison acceleration signal ar.

Next, the operation of the comparison function generator 2 shown in FIG. 2 will be described.

At the initial stage, the count pulse generator 16 is stopped and the counter 17 is reset to zero.

In this state, the target position setting value X represents the new movement target point.

is input at time t=to (see FIG. 4a), at the same time, the count pulse generator 16 starts generating count pulses P1 at a predetermined period, and the counter 17 starts counting operation.

At this time, the target position set value X is output from the subtracter 12.

and the comparison position signal The ROM 15 outputs speed setting data D3 that changes according to the value of D2 as shown in FIG. 4b.

On the other hand, since the counter 17 performs a simple addition operation, its count output data D4 increases linearly with the passage of time t, as shown in FIG. 4C.

These two data D3 and D4 are selectively taken out by the comparator 18 and the multiplexer 19 as described above.

That is, the output signal S2 taken out from the multiplexer 19
0 means that data D4 is taken out immediately after the start of movement, and when data D4 becomes larger than data D3 after a certain time t1, for example, data D3 is taken out.

Therefore, the composite data S20 taken out from the multiplexer 19 becomes as shown in FIG. 4d.

Therefore, the comparison speed data selected by the multiplexer 19 never exceeds the maximum acceleration and maximum speed predetermined in the ROM 15.

Specifically, in FIG. 4b, the relationship between D2 and D3 is a square root function, and in this case, the deceleration portion in FIG. 4d is a constant acceleration, that is, linear.

Therefore, at the settling time t2, the acceleration suddenly changes (becomes zero), which may induce vibration.

Therefore, it is convenient that the functional relationship between D2 and D3 incorporated in the ROM 15 is set to an appropriate function that does not actually induce vibration.

The comparison speed data obtained in this way is converted into an analog signal S9 by the D/A converter 20, and then the V/F
It is converted by the converter 21 into a pulse signal P2 whose frequency changes according to the value of the comparative speed data, and the pulse signal P2 is converted into a pulse signal P2 whose frequency changes according to the value of the comparison speed data.
is subtracted or added by this pulse signal P2.

As a result, a comparison position signal X, which is an integral value of comparison speed data, is obtained.

Note that when Xo=Xr, the stop control signal S7 becomes "1".
'', the oscillation of the V/F converter is stopped, and therefore the movement of the counter is also stopped.

If there is no stop control signal S7, the V/F converter will actually oscillate a little even when the analog signal S is "0", causing an error.

On the other hand, the analog signal S9 is an analog version of the comparison speed data, which is output as the comparison speed signal Vr.

At this time, the polarity is also inverted by the multiplexer 23 depending on whether the data output from the subtracter 12 is positive or negative and is output.

That is, for example, if you have been moving in the positive direction and the data D1 is still positive, you have not yet reached the target point, so the analog signal S9 will be output as is, and if the data D1 becomes negative, then the analog signal S9 will be output as is. For example, since the target point has been exceeded, the analog signal S, is transferred to the inverter 22.
The polarity is inverted and output via the .

The output from the multiplexer 23 is differentiated by the differentiating circuit 24 and output as a comparison acceleration signal ar.

As mentioned above, according to the comparison function generator 2, it is possible to generate the optimal comparison position function, comparison speed function, and comparison acceleration function that match the performance of the servo mechanism from the difference between the current point and the target point. Therefore, the control operation of the closed loop control device 3 shown in FIG. 1 can be performed extremely stably and quickly.

According to the present invention, as described above, it is possible not only to accurately instruct the amount of movement, but also to instruct the movement speed and acceleration at optimal values commensurate with the performance of the servo mechanism, thereby creating an almost ideal servo mechanism. can be controlled.

This makes it possible to reduce the position deviation and speed deviation to almost zero, reduce the dynamic range, facilitate the design of the control system, and obtain a highly stable control device with extremely high tracking performance. be able to.

[Brief explanation of the drawing]

Figure 1 is a block diagram of one embodiment of the present invention, Figure 2 is a detailed block diagram of the comparison function generator shown in Figure 1, and Figure 3 is the input/output of the absolute value detection circuit shown in Figure 2. Characteristics, Figure 4a
4d to 4d are characteristic diagrams of various parts for explaining the operation of the comparison function generator shown in FIG. 2. 1: Servo control device, 2: Comparison function generator, 3: Closed loop control device, a r 'comparison acceleration signal, ■ r: Comparison speed signal, Xo: Target position set value, Xl: Comparison position signal.

Claims (1)

[Claims] 1. In a servo control device of a closed-loop positioning control system that constantly performs position feedback, an acceleration that does not exceed the maximum acceleration and maximum speed of the device when controlling the positioning of a controlled object from the first position to the second position. means for generating a comparison position function having a velocity component and a velocity component; means for generating a comparison velocity function based on the comparison position function; means for generating a comparison acceleration function based on the comparison position function; A servo control device comprising: a closed loop control device that performs a position control operation in accordance with the comparison speed function and the comparison acceleration function.